Methods for detecting ice and liquid water on surfaces
First Claim
1. A method for detecting ice on a surface comprising:
- acquiring a reflectance spectrum of light reflected off of a surface to be tested;
calculating a midpoint wavelength of a transition in the reflectance spectrum;
comparing the midpoint wavelength to a decision threshold wavelength; and
indicating the presence of ice on the surface if the midpoint wavelength is greater than the decision threshold wavelength.
2 Assignments
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Accused Products
Abstract
Methods for detecting the presence or absence of ice or liquid water on surfaces are provided. In a first embodiment of the invention, a reflectance spectrum from a surface to be tested is measured using any suitable near-infrared optical system. The midpoint wavelength of the transition or step of the measured reflectance spectrum near 1.4 microns is calculated, and compared to a decision threshold wavelength. If the midpoint wavelength is less than the decision threshold wavelength, the presence of liquid water on the surface is indicated. If the midpoint wavelength is greater than the decision threshold wavelength, the presence of ice is indicated on the surface. In a second embodiment of the invention, at least three reflectance levels are measured at three wavelengths, and a dimensionless decision function is applied to the measured reflectance levels. Output of the decision function is compared to at least two pre-defined ranges. If the output is within a first range, the presence of liquid water on the surface is indicated. If the output is within a second range, the presence of ice on the surface is indicated. If the output is between the pre-defined ranges, the absence of ice or water on the surface is indicated.
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Citations
56 Claims
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1. A method for detecting ice on a surface comprising:
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acquiring a reflectance spectrum of light reflected off of a surface to be tested; calculating a midpoint wavelength of a transition in the reflectance spectrum; comparing the midpoint wavelength to a decision threshold wavelength; and indicating the presence of ice on the surface if the midpoint wavelength is greater than the decision threshold wavelength. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for detecting liquid water on a surface comprising:
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acquiring a reflectance spectrum of light reflected off of a surface to be tested; calculating a midpoint wavelength of a transition in the reflectance spectrum; comparing the midpoint wavelength to a decision threshold wavelength; and indicating the presence of liquid water on the surface if the midpoint wavelength is less than the decision threshold wavelength. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A method for detecting whether ice or liquid water is present on a surface comprising:
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measuring three reflectance levels of light reflected off of a surface in three wavelength bands; calculating a midpoint wavelength of a transition using the three reflectance levels; indicating the presence of ice on the surface if output of the decision function falls within a first pre-determined range; and indicating the presence of liquid water on the surface if output of the decision function falls within a second pre-determined range. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
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48. An apparatus for detecting the presence of ice or liquid water on a surface comprising:
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a light source for illuminating a surface to be tested; a detector for detecting at least three reflectance levels Ra, Rb, and Rc at three wavelengths a, b, and c; and a signal processor having a decision function for calculating a midpoint wavelength of a reflectance spectrum based upon the at least three reflectance levels Ra, Rb, and Rc and determining the presence of ice or water using the midpoint wavelength. - View Dependent Claims (49, 50, 51, 52, 53, 54, 55, 56)
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Specification